Fisherman{40 s water temperature locating apparatus

ABSTRACT

Fishing apparatus for locating a desired water temperature layer in temperature-stratified fishing waters, the apparatus including submersible temperature sensing means and desired temperature signal means. In the preferred electrical embodiment, the temperature sensing means is an electrical switch having a bimetallic coil element as a temperature responsive contact, the other contact being adjustable to preselect the desired temperature, the contacts being connected by leads to the signal means comprising a modified flashlight providing a circuit including a battery power source and a lamp. The apparatus permits preselecting the desired temperature by setting the adjustable contact and locating the desired temperature layer on the first lowering of the adjusted switch, which is normally open at surface temperatures above the preselected temperature, through the progressively colder water until the bimetal closes the switch when the desired temperature is first reached, as indicated by the lighted lamp.

United States Patent [191 Potoroka, Sr.

[ FISHERMAN'S WATER TEMPERATURE LOCATING APPARATUS [76] Inventor: WalterPotoroka, Sr., 3505 Adams Rd., Lake Orion, Mich. 48035 [22] Filed: Nov.9, 1970 [21] Appl. No.: 87,888

Related U.S. Application Data [63] Continuation-impart of Ser. No.615,829, Feb. 13,

1967, Pat. No. 3,540,023.

[52] U.S. Cl 340/2271, 43/17, 340/283 [51] Int. Cl Alk 97/12 [58] Fieldof Search 340/227.l, 283; 43/17.l, 17, 4

[56] References Cited UNITED STATES PATENTS 3,561,267 2/1971 Costello43/4 1,062,292 5/1913 McNab 340/227.l

Primary Examiner-Donald J. Yusko Assistant Examiner-Glen R. Swann, lll

[ Oct. 2, 1973 [5 7] ABSTRACT Fishing apparatus for locating a desiredwater temperature layer in temperature-stratified fishing waters, theapparatus including submersible temperature sensing means and desiredtemperature signal means. In the preferred electrical embodiment, thetemperature sensing means is an electrical switch having a bimetalliccoil element as a temperature responsive contact, the other contactbeing adjustable to preselect the desired temperature, the contactsbeing connected by leads to the signal means comprising a modifiedflashlight providing a circuit including a battery power source and alamp. The apparatus permits preselecting the desired temperature bysetting the adjustable contact and locating the desired temperaturelayer on the first lowering of the adjusted switch, which is normallyopen at surface temperatures above the preselected temperature, throughthe progressively colder water until the bimetal closes the switch whenthe desired temperature is first reached, as indicated by the lightedlamp.

10 Claims, Drawing Figures Patented Oct. 2, 1913 3,763,481

2 Shea hex-Sheet 1.

Patented Oct. 2, 1973 3,763,481

2 Sheets-Sheet 2 I N VEN TOR.

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1 FISHERMAN'S WATER TEMPERATURE LOCATING APPARATUS This application is acontinuation-in-part of my parent application Ser. No. 615,829 filed onFeb. 13, 1967, now U.S. Pat. No. 3,540,023, and entitled FISH- ERMANSWATER TEMPERATURE LOCATING APPARATUS.

Brief Summary of the Invention The invention will be best understood byreference to the following published materials:

1. How to Find Fish in Summer, Outdoor Life, July,

1966, by Wynn Davis.

2. Fishermans Encyclopedia, edited by Dr. Ira N.

Gabrielson.

3. Thermal Stratification in Reservoirs by F. W. Kittrell (Presented atthe Symposium on Streamflow Regulation for Quality Control April 3-5,1963, Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio).

Davis points out the problems of a summertime fisherman, gives some ofthe reasons for these problems, inluding a discussion of thethermocline, and makes suggestions for overcoming these problems. TheKittrell report presents scientific evidence of the thermalstratification referred to by Davis, and the Fishermans Encyclopedia, inaddition to verifying the Davis article, states some of the specificpreferred water temperatures for the various species of game fish.

In summary, it can be stated that the summertime fisherman is at adefinite disadvantage and increases his chances of catching a particularspecies of fish, particularly in lakes subject to thermalstratification, by fishing where the preferred temperature level forthat particular species, regardless of depth, intersects the lakebottom, where the food and cover are found.

Fishermens thermometers are already available, but they are either tooexpensive or have certain disadvantages. Ideally, the fisherman shouldknow what temperature he is seeking and be able to find the desiredtemperature the first time he lowers the temperature responsive deviceinto the water. The electronic water thermometer shown in the article byDavis has this capability, but it is too expensive for most fishermen.the maximum-minimum thermometer mentioned in the Fishermens Encyclopediais somewhat less expensive, but it has the disadvantage that it must beraised to the surface for reading; that is, it must be lowered andraised a number of times in order to locate the desired temperature. Thesame disadvantage is characteristic of other less expensive fishermensthermometers that are available.

For example, the instructions for one relatively inexpensive fishermensthermometer read, 1. Attach to line; let sink to bottom or desireddepth. 2. Hold at bot tom or desired depth for 30 seconds; return tosurface. 3. Read depth at top of water column; temperature off temp.plate. 4. lnvert instrument; press valve to release water. Shake allwater out. These instructions also include the Temperature PreferenceRanges for most game fish. However, there is at least one disadvantageto this device, that being that the instrument must be raised to thesurface to observe the temperature. Otherwise, there is no way ofknowing what the temperature is.

Accordingly, a main object of this invention is to provide aninexpensive fishermans thermometer apparatus that may be set for thedesired temperature before it is lowered into the water and that willgive an electrical or mechanical signal on the first lowering of thedevice when the desired temperature is first reached, the device havingsufficient weight so that it can then be moved about the lake, withoutraising the same, until its engagement with the lake bottom is felt.

Another object of the invention is to provide such apparatus wherein thetemperature sensing element is a bimetallic element.

Another object of the invention is to provide such apparatus operatingon an electrical principle.

Another object of the invention is to provide such apparatus wherein thedesired temperature signal is a lamp. Still another object of theinvention is to provide such apparatus wherein the desired temperaturesignal portion may be an ordinary flashlight, which fishermen shouldhave available in any event, modified for use as part of the apparatus,and for other practical uses, but still capable of its original use as aflashlight, either separate from or attached to said apparatus.

A still further object of the invention is to provide such apparatuswherein the desired temperature signal is mechanical, rather thanelectrical.

Another object of the invention is to provide such ap paratus whereinthe temperature sensing portion is sufficiently weighted to serve as alake bottom finding device.

Another object of the invention is to provide such apparatus wherein thetemperature sensing element is enclosed to protect the same from damage,the enclosure having an opening therein to enable the free flow of watertherethrough for continuous contact with the temperature sensingelement.

Another object of the invention is to provide such apparatus wherein thedesired temperature setting device is permanently marked with atemperature scale and/or a fish species preferred temperature scale sothat such necessary information is always at hand.

Still another object of the invention is to provide such apparatushaving independent means for determining the temperature at any depth towhich the temperature responsive was lowered, thereby making theapparatus better suited for purposes such as determining thermoclinedepths.

Another object of the invention is to provide such apparatus havingmeans for calibration thereof during its assembly in manufacture.

Another object of the invention is to provide such apparatus wherein thebimetallic element is a bimetal coil.

A further object of the invention is to provide such apparatus whereinthe bimetallic element has a corrosion resistant thin non-metallic ormetallic coating.

Another object of the invention is to provide such apparatus whereinelectrical current does not pass through the bimetallic element; thatis, the bimetallic element closes the switch, but is not part of theelectrical circuit.

These and other objects and advantages of the invention will become moreapparent upon reference to the detailed description below and theattached drawings.

Brief Description of the Several Views of the Drawings FIG. 1 is aschematic illustration of the preferred embodiment of a completeapparatus embodying the invention, the flashlight signal portion beingshown in cross section and the temperature responsive portion to belowered into the water being shown in perspective;

FIG. 2 is a cross sectional view taken on the plane of line 2-2 of FIG.1 and looking in the direction of the arrows;

FIG. 3 is an exploded perspective view of two elements of thetemperature sensitive element shown in FIG. 1;

FIG. 4 is a cross sectional view taken on the plane of line 4-4 of FIG.1 and looking in the direction of the arrows;

FIG. 5 is a perspective view of a modification of the invention whereinthe desired temperature signal is produced by mechanical, rather thanelectrical, means.

FIG. 6 is a view, with portions thereof cut away and in cross section,illustrating a somewhat simpler modification of the temperatureresponsive portion of the invention shown in FIGS. 1-4;

FIG. 6a is a slightly enlarged fragmentary portion of FIG. 6,illustrating a modification of the invention.

FIG. 7 is a perspective view of another possible arrangement of thetemperature sensing portion.

FIG. 7a is an enlarged fragmentary portion of FIG. 7, illustratinganother modification of the invention.

FIG. 8 is a side elevational view of still another embodiment of theinvention, specifically the temperature sensitive portion thereof.

FIGS. 9-12 are cross-sectional views taken on lines 9-9, 10-10, 11-11and 12-12 of FIG. 8, looking in the direction of the arrows.

FIG. 13 is a cross-sectional view taken on the plane ofline 13-13 ofFIG. 9, looking in the direction of the arrows.

Detailed Description Referring now to the drawings in greater detail,and particularly to FIGS. 1-4, the apparatus 10 includes, in itspreferred embodiment, a temperature sensing portion or assembly 12 and asignal portion or assembly 14.

Since it is a common device well suited, with but slight modification,for purposes of the invention, the signal portion of device 14, which isan ordinary flashlight, will be discussed very briefly.

A common flashlight 14 includes a hollow cylindrical metal body orhousing 16 having a closed end 18 and a flared open end formed withthreads 20. The housing contains a metal spring 22, and it is usuallyloaded with two batteries 24. A non-conductive or insulating reflector26 is inserted into the open end of the body, the reduced diameterportion 28 of the reflector being fitted with an annular stationarymetal contact or switch element 30 into which the metal base of the lamp32 is threaded. A lens 34 and a threaded cap 36 are then fitted on theopen end of the body 16. The body is provided with a movable metalswitch element 38 that includes a movable contact 40 for engagingstationary contact 30, at which time a circuit is completed within thehousing 16 to energize the lamp 32. The flashlight 14 is shown in theopen circuit position in FIG. 1, movable contact 40 being out ofengagement with stationary contact 30.

The details of construction of other well-known flashlights may vary,but the principle of operation is the same. With the contact 40 in theopen or off position shown, other means may be provided to close acircuit and energize the lamp 32, adapting the flashlight for otheroften needed uses, such as for testing low voltage circuits or as a lowvoltage power supply, or use as the signal portion 14 of the invention.The reader undoubtedly can recall many instances where he was in need ofa low voltage power source to conduct some kind of a test or experimentand had to make one up. The modified flashlight proposed herein providesjust such a handy device.

A suitable modification for this purpose may be to provide a firstterminal comprising means such as a screw 42 and two nuts 44 at theclosed end of the body 16 and a second similar terminal near the lampend of the body, the second terminal comprising two nuts 46 on a screw48 having a contact 50 continuously in engagement with stationarycontact 30, the contact 50 and screw 48 being insulated from the body 16by a non-conducing rubber or other grommet 52. With the switch 38 in theoff or open circuit position, the lamp 32 will not light due to theinsulator 52, unless the circuit including terminals 42 and 48 areconnected by some other switch means. Thus, in the condition described,the flashlight 14 may be used for its originally intended purpose, or itmay be used for these other purposes. Obviously, simpler, quidk-connecttype terminals could be substituted for terminals 42 and 48, and themodification could be made in other equivalent ways.

It is also obvious that some other equivalent signal device could beprovided. However, flashlights are already available for this simplemodification, and a fisherman should always have a flashlight among hisitems of equipment, for obvious reasons including emergencies. If hedoesnt already have one, the invention will provide one, or it willprovide a spare one.

The temperature responsive or sensing portion 12 of the apparatus 10may, of course, be constructed in a number of ways. In the preferredembodiment shown, the device 12 is constructed around a hollow injectionmolded plastic or other non-conducting body 54 formed essentially in amanner shown in perspective by FIG. 3, with one thicker wall 56 having awedge groove 58 formed therein, the groove extending to a steppedportion or abutment 60 having an unthreaded passage 62 formed therein. Astrip of metal or other conducting material 64 is secured at the base ofthe groove 58, one end 66 (FIG. 1) of the strip extending beyond the topend of the body 54.

Another main element of the device 12 is the metallic or otherconducting block 68 having a sloped side 70, a wedge projection 72fitting and slidable in the wedge groove 58, a threaded passage 74formed therein and an indicator or pointer 76 extending from the sidethereof opposite the sloped side 70. Alternatively, the block 68 may beof plastic material, with conducting surfaces molded therein.

As shown in FIG. 2, a plastic or other non-conducting bolt or screw 78having a knurled head 80, an unthreaded portion 82 and a threaded endportion 84 is disposed in the unthreaded passage 62 so that it may berotated freely, the bolt being retained axially by flange means 86. Thethreaded end 84 of the screw is disposed in the threaded passage 74 inthe block 68, with a coil spring 88 between the portion 60 and the block68. Thus, rotation of the screw causes the block 68 to be moved alongthe groove 58 in a direction dependent upon the direction of rotation ofthe screw.

The pointer 76 is disposed in a groove 90 (FIG. 1) formed in the strip64 and the bottom of groove 58, the outer surface of body 54 on one side92 of the groove being conveniently molded or otherwise permanentlymarked with indicia of temperature and on the other side 94 thereof withindicia of preferred temperatures for specific fish species so that suchnecessary information is always at hand. It will be apparent, then, thatthe pointer 76, and the block 68, can be set to any specific desiredtemperature (species).

A temperature responsive bimetallic strip 96 and a terminal 98 (FIG. 2)are secured by any suitable means, such as rivets 100, to the inner wallof the body 54, opposite the sloped side 70 of the block 68. The strip96 may be selected so that at the highest expected summertime ambienttemperature the free end of the strip is disposed substantially adjacentthe wall 102, the strip moving towards the dotted line position 104 astemperature drops upon lowering thereof into a stratified lake.

It can now be seen that the slope 70, a bimetallic strip 96 and a threadpitch of screw 78 can be selected such that the free end of the strip 96repeatedly engages the block 68 precisely at the temperature to whichthe pointer 70 is set, providing an electrically conductive path fromthe terminal 98, through the strip 96 and block 68 and then to the end66 of the conductor strip 64.

If lead wires 106 and 108 of suitable length are connected betweenterminals 42 and 66 and terminals 48 and 98, respectively, the pointer76 is set to some temperature, 70 for example, and device 12 is loweredinto a stratified body of water during the summertime, the temperaturewill drop and the bimetal 96 will distort until at 70 it engages thesloped surface 70, at which time a circuit will have been completed andlamp 32 will be energized, indicating that the desired temperature, 70,has been reached. It should be noted that plastic body 54 has a passagetherethrough so that the bimetallic strip 96 is always in contact withchanging water temperature, with the strip 96 being at all timesprotected from damage.

Having found the desired temperature (species) layer, the fisherman canthen slowly move his boat until the device 12 engages the lake bottomand fish the botton in that area. Preferably, a steel or other weight110 is added to enable penetration of weed beds and facilitateaccurately locating thelake. bottom. Spaced markers 111 or other meansmay be employed to mark off distances along the leads 106-108, if it isdesired to determine the depth at which the desired temperature exists.However, the fisherman is normally seeking a temperature, rather than adepth.

At a minimum of additional cost, a second bimetallic element 112 may besecured within the body 54 in a position for the free end thereof toreposition a lever 114 pivoted on a pin 116 extending through the wallof body 54 and having a pointer 1 18 traversing a temperature scale 120(FIGS. 1 and 4). That is, before the device 12 is lowered into thewater, the pointer 118 is set to the higher end of the scale; as thedevice 12 is lowered, the pointer is moved by the element 112 to andleft at the lowest temperature reached, which temperature can be readwhen the device 12 is raised to the surface.

While the device 12 is shown as a square or rectangular tube structure,it may, of course, be made in any shape, such as cylindrical, and thestructural details may be varied considerably without departing from theprinciple of operation thereof. Furthermore, the apparatus 10 need notbe electrical.

The device 122 shown by FIG. 5 can also be set to a particulartemperature and will provide a signal to the fisherman when the desiredtemperature is reached. However, the operation and the signal are notelectrical; rather, they are mechanical, and device 122 is completeitself. Device 122 is shown as a hollow, boxlike structure containing aspring-driven motor 124 wound by a sealed key 126 and driving aneccentric weight 128.

A bimetallic element 130 is mounted on an axially adjustable pin 132,adjustment being provided by means of a screw 134 having a pointer 136traversing a temperature and/or a species scale 138. The motor 124 maybe retained in the wound condition by a ratchet 140 and pawl 142, thelatter being pivoted on fixed pin 144 and pivotally connected to thesealed trigger 146.

By adjustment of the screw 134, the bimetallic element 130 can be madeto depress trigger 146 at the temperature to which the pointer 136 isset and release the pawl 142. As the motor unwinds, the weight 128 willbe rotated, resulting in a wabbling motion, much like that of a hookedfish, of the device 122 felt in the line 146 attached to the stern 148.The device may require a weight 150 to intensify the signal and assistin locating the lake bottom.

Other mechanical devices are, of course, possible, the importantrequirements being that the device can be pre-set to a desiredtemperature and capable of providing a pull on the line or some othersignal when the desired temperature has been reached so that the deviceneed not be raised to observe the temperature. For example, knowntemperature responsive devices capable of applying a greater force thana bimetallic element may be combined with a spring and made to trip aweight, resulting in a substantial mechanical signal.

FIG. 6 illustrates a somewhat simpler version 152 of the temperaturesensor 12 shown by FIG. 1. The body 154 may be cylindrical orrectangular and formed of molded plastic, with a recess 156 on one sidethereof. A bimetallic element 158 is secured at one end to the body 154,as by screws or rivet 160, so that it moves to the dotted line positionas temperature decreases. A metal screw 162 having a metal contact 164and a knurled head 166 is received in a threaded passage including ametallic element 168. Lead wires 170 and 172, corresponding to leadwires 106 and 108, are secured to rivet and element 168, respectively,and they extend beyond the body 154 for connection to the signal device14. A temperature and/or species scale 174 is marked on the body, thedevice being set before lowering into the water by positioning thecontact 164 at the desired temperature and the operation being similarto that of the device 12 of FIG. 1. A weight 115 may be screwed into thebottom of the body 154.

FIG. 7 merely illustrates another possible arrangement of the conductingelements of a modified temperature sensing device 176, it beingunderstood that these elements would be suitably mounted in a supportingstructure. The bimetallic element 178 has a lead 180, and the free end182 thereof moves toward the metal cam 184 mounted to rotate with themetal shaft 186 having a pointer 188 and mounted in a metal sleeve 190to which a lead 192 is connected. The cam is contoured so that thetemperature at which it is contacted by the bimetallic elementcorresponds to the position of the pointer 188 on the temperature and/orspecies scale 194, the device being connected to a signal device such asdevice 14 and operating in a manner similar to device 12.

It should be apparent from the above description that there has beenprovided novel, simple and inexpensive means for accurately locating,with certainty, desired temperature layers in a stratified body ofwater, without having to raise the device to observe the temperaturesensing device itself and making several attempts to locate the desiredtemperature. The device can be either electrical or mechanical, and itcan be provided with additional means for indicating the minimumtemperature to which the device has been lowered. The device produces asignal only when and as soon as the desired temperature is located, thesignal being of a character such as to be perceptible to the fishermanwithout observing a continuously reading temperature scale, such as in atemperature calibrated electric meter, which is expensive and requirescareful handling, and without raising any part of the device to read athermometer. In fact, in the embodiments shown, the signal isperceptible even in darkness, as for night fishing. Further, an electricsignal device has been provided by simply modifying an ordinaryflashlight, the modified flashlight also having other practical uses.

It will be understood that the main feature of the flashlightmodification is the provision of an additional circuit portion includinga pair of terminals accessible for connection to an external circuitportion, it being possible to arrange the additional circuit so that thelamp may be excluded, if so desired, as when the flashlight is used notas a circuit tester but merely as a convenient power source package andthe lamp is not required or desired. For example, with the modificationshown in FIG. 1, a simple conducting screw member could be substitutedfor the lamp screw base 25 to provide a direct connection between thecontact 30 and the adjacent battery, but other arrangements arepossible, perhaps even by redesign of the switch member 38. Obviously,terminal 48 should be constructed and arranged so that the additionalcircuit portion cannot itself be closed by an accidental connectionbetween the housing 16 and the terminal 48, as might occur if theflashlight were resting on a conducting surface with terminal 48touching the same.

The embodiment of FIG. 7a illustrates that the bimetallic element 178may have thereon a flash deposit or coating 181 of copper or otherconducting metal so as to lend corrosion resistance to the bimetal ifthat is desired.

FIG. 6a illustrates a structure wherein the bimetallic element 158 has athin pliable non-conducting coating 159 for corrosion resistance, ifthat is desired, with a contact element 161 secured thereto, the lead170 being connected to the conducting contact element 161. In thisconstruction, the current does not pass through the bimetal when theswitch elements 161 and 164 are closed, which may be desirable.

Additionally, FIG. 6a illustrates means for factory calibration tocorrect for bimetal temperature response tolerances. The body 154 isformed with a bore of cavity 155 receiving, with a relatively close orpress fit, the

mating member 153 to which the bimetal element 158 is attached, as byrivets 160, or any other suitable manner, such as gluing.

The calibration procedure would be to set the contact to the selectedtemperature on the scale 174, soak the mechanism in the selectedtemperature and then adjust element 153 within cavity 155 so that thecontact 161 just engages contact 164. The press fit may be relied uponto maintain the fixed end of the bimetal element so that subsequentrecalibration is possible, or, in this case the thermoplastic parts maybe heat sealed.

FIGS. 8-13 illustrate a possible production version of the varioustemperature responsive portion structures and modifications heretoforedisclosed and described, all features in FIGS. 1-13 beinginterchangeable.

In this version of portion 12, the main body 200 is preferably formedfrom a non-conducting injection moldable material, the body having a web202 (FIG. 13) closing one end thereof and a hollow cylindrical portion204 depending from the web portion, which is formed with a bore 206formed therethrough. The web 202, which may be formed as a separateelement, is formed with a threaded passage adapted to receive a screw208 that adjustably retains a bracket 210 at the slot 212 formedtherein, the bracket having a depending portion 214.

A molded or other non-conducting shaft 126 extends, with clearance,through the passage 206, the shaft having an enlarged portion 218 formedwith a slot 220. The inner diametrically extending end 222 of thebimetal coil 224 (FIG. 11) is positioned in the slot 220, while theouter radially extending end 226 thereof is secured, as by rivets 228 orin any other suitable manner, to the depending portion 214 of bracket210. The other end 230 (FIGS. 12 and 13) of the shaft is received in abore 232 formed in the hub end 234 of a non-conducting arm 236 having acontact 238 thereon.

It will thus be seen that as the temperature of the coil 224 varies, thecoil winds up or unwinds. Since the outer end of the coil is fixed, thecoil rotates shaft 216 and the arm 236 so as to move the contact 238. Inthis case, the coil is designed to wind up as temperature decreases, andto unwind as temperature increases.

Teflon washers 240 (FIG. 13) or other low friction bearings may beprovided to minimize frictional resistance to the rotation of shaft 216.

A circular temperature selecting plate 242 (FIGS. 8-13) has one flange244 conforming to the annular outer shape of the body 200 and a flatflange 246 resting on the upper surface of web 202. The plate 242 isformed with a slot 248 receiving a screw 250 by which the plate 242 issecured in the position for the desired temperature, as indicated by end252 of the plate 242 on the temperature scale 254. The plate 242 isformed with an integral upstanding tab 241 that has a contact 243secured therethrough.

A preferably injection molded hollow cap 256, having a slot 258 formedon one side thereof receiving and allowing adjustment of the plate 242,is secured in any suitable manner, such as by gluing, to the main body200, as shown in FIG. 8. Leads 260 and 262 are connected to contacts 238and 243, respectively, and they extend through the opening 264 in thecap 256, for attachment to the signal portion as shown in FIG. 1. Acircular lead, steel or other weight 266 (FIG. 8) is secured in anysuitable manner within the open end of the body 200, the weightpreferably having a concave end 268 for directing the lake water throughthe openings 270 as the device 12 is lowered, as shown by the arrows.The decreasing temperature water flows up through the hollow body 200and then out the sloped openings 272, the sloped surface 274 (FIG. 13)assisting in directing the water through the openings 272.

Several embodiments of the invention have been shown and described insuch clear and concise terms as to enable anyone skilled in the art topractice the same. Other modifications may be possible, and nolimitations are intended, except as recited in the appended claims.

What I claim as my invention is:

l. A device adapted for use by a fisherman to locate a particulardesired water temperature layer in a thermally stratified fishing lake,said device comprising first means responsive to temperatures within therange of decreasing water temperatures expected to be encountered inlowering the same from the lake surface toward the lake bottom, saidfirst means having means for calibration thereof upon assembly duringmanufacture thereof, said first means also having means for adjustmentthereof prior to lowering the same by suitable means to select saidparticular desired water temperature layer and second means cooperatingwith and actuated by said first means through said lowering means forautomatically producing an instantaneous sensory signal when said firstmeans first attains said selected temperature, said apparatus beingconstructed so that said sensory signal is of a character such as to beperceptible to the fisherman without observing a temperature scale andwithout requiring raising said first means to the lake surface todetermine the temperature.

2. A device such as that recited in claim 1, wherein said first andsecond means comprise elements of a single electric circuit means.

3. A device such as that recited in claim 2, wherein said electriccircuit means includes one temperature responsive electric currentswitching means, said device being free of other switches.

4. A device such as that recited in claim 3, wherein said calibrationmeans includes means for adjusting the operation of said switchingmeans.

5. A device such as that recited in claim 3, wherein said first meansincludes a temperature responsive bimetal element.

6. A device such as that recited in claim 5, wherein said deviceincludes a body, said bimetal element is a bimetal coil having one endthereof adjustably secured on said body to provide said calibrationmeans, the other end of said coil having a radially extending armassociated therewith, the outer portion of said arm experiencingmovement through an are upon response of said coil to changes of watertemperature and including a first electrical contact, a secondelectrical contact on said body, said second electrical contact beingadjustably secured on said body so as to enable selection, by variationof the initial distance between said contacts, of the temperature atwhich said first and second contacts will come into electricalengagement.

7. A device such as that recited in claim 1, wherein said first meanscomprises a first temperature responsive bimetallic element and a secondmanually adjustable element, said first and second elements havingformed thereon first and second electrical contact elements,respectively, said contact elements experiencing progressivelyincreasing proximity as said first means is lowered throughprogressively decreasing water tem-- perature until said contacts makeelectrical contact when said selected water temperature is firstreached, said signal means including an electrical power source and aninstantaneous on-off electrical signal means, said lowering meanscomprising electrical leads for providing an electrical circuit betweensaid second means and said contacts, whereby said signal will beproduced when said contacts first make electrical contact.

8. A device such as the recited in claim 5, wherein said electriccircuit means bypasses said bimetal element.

9. A device such as that recited in claim 5, wherein said bimetalelement is formed with a continuous outer coating isolating the bimetalinterface from the environment.

10. A device such as that recited in claim 6, wherein said body is inthe form of a hollow cylindrical housing so as to accommodate said coiland to enable the temperature selecting adjustment of said secondelectrical contact by movement thereof through an arc.

1. A device adapted for use by a fisherman to locate a particulardesired water temperature layer in a thermally stratified fishing lake,said device comprising first means responsive to temperatures within therange of decreasing water temperatures expected to be encountered inlowering the same from the lake surface toward the lake bottom, saidfirst means having means for calibration thereof upon assembly duringmanufacture thereof, said first means also having means for adjustmentthereof prior to lowering the same by suitable means to select saidparticular desired water temperature layer and second means cooperatingwith and actuated by said first means through said lowering means forautomatically producing an instantaneous sensory signal when said firstmeans first attains said selected temperature, said apparatus beingconstructed so that said sensory signal is of a character such as to beperceptible to the fisherman without observing a temperature scale andwithout requiring raising said first means to the lake surface todetermine the temperature.
 2. A device such as that recited in claim 1,wherein said first and second means comprise elements of a singleelectric circuit means.
 3. A device such as that recited in claim 2,wherein said electric circuit means includes one temperature responsiveelectric current switching means, said device being free of otherswitches.
 4. A device such as that recited in claim 3, wherein saidcalibration means includes means for adjusting the operation of saidswitching means.
 5. A device such as that recited in claim 3, whereinsaid first means includes a temperature responsive bimetal element.
 6. Adevice such as that recited in claim 5, wherein said device includes abody, said bimetal element is a bimetal coil having one end thereofadjustably secured on said body to provide said calibration means, theother end of said coil having a radially extending arm associatedtherewith, the outer portion of said arm experiencing movement throughan arc upon response of said coil to changes of water temperature andincluding a first electrical contact, a second electrical contact onsaid body, said second electrical contact being adjustably secured onsaid body so as to enable selection, by variation of the initialdistance between said contacts, of the temperature at which said firstand second contacts will come into electrical engagement.
 7. A devicesuch as that recited in claim 1, wherein said first means comprises afirst temperature responsive bimetallic element and a second manuallyadjustable element, said first and second elements having formed thereonfirst and second electrical contact elements, respectivelY, said contactelements experiencing progressively increasing proximity as said firstmeans is lowered through progressively decreasing water temperatureuntil said contacts make electrical contact when said selected watertemperature is first reached, said signal means including an electricalpower source and an instantaneous on-off electrical signal means, saidlowering means comprising electrical leads for providing an electricalcircuit between said second means and said contacts, whereby said signalwill be produced when said contacts first make electrical contact.
 8. Adevice such as the recited in claim 5, wherein said electric circuitmeans bypasses said bimetal element.
 9. A device such as that recited inclaim 5, wherein said bimetal element is formed with a continuous outercoating isolating the bimetal interface from the environment.
 10. Adevice such as that recited in claim 6, wherein said body is in the formof a hollow cylindrical housing so as to accommodate said coil and toenable the temperature selecting adjustment of said second electricalcontact by movement thereof through an arc.